Truly excellent answers above, all dead on. Can you 'buy' flies on line at half (or less) the price? Without question. Will they be well tied? With little exception.

But what you're trading for a twenty dollar bill is 'Information.' (For Jollies, watch the old TV series "The Prisioner.")

My only toss in is Google Earth'ing the area(s) you want to fish. Amazing what you'll find in the way of 'access' you'd never (or spend hours) looking for "Boots on the ground."

Here in Southern Oregon the current view is 2010 (or 11?) so you're looking at reel time (spelling pun intended). Print photo(s), and off you go. Gather you can do a lat/long cross hairs for your GPS, but haven't figured out how to do that yet (GPS input).

Lots of great advise given already. The only thing I would add is to learn their names and listen more than speak. If you show genuine interest most people will be more than happy to help you out.
Welcome to the forum.

a tweed jacket and a pipe will help. Just messing with you obviously, welcome to the forum and good luck!

One more piece of real advise. If you have a productive day after stopping in for advise stop back and let them know. The fact that they put a new guy on some fish will probably be more rewarding than the $15-$20 spent in the shop.

Buy the Abel nippers, and they'll tell you all you want to know. And for heaven's sake, if you're wearing your tweeds and carrying your pipe, make sure you're packing your cane rod, a plastic rod would just be a major fishing fashion faux pa.
Seriously, guys in fishing sales, love to talk fishing, when we can't be fishing ourselves. No worries.